Difference in microstructure of Zr41Ti14Cu12.5Ni10Be22.5 glasses prepared in a 52 m drop tube and by water quenching

A 52 m drop tube has been used to solidify bulk-glass-forming Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 alloy. Glassy balls with different sizes solidified from the droplets whose structural features, glass-transition behaviour and crystallization kinetics have been investigated. The results indicate that the apparent activation energies of the glass transition and main crystallization reaction are significantly different from those of samples prepared by water quenching. The structural difference between the two types of glassy specimen is revealed by compression studies and in situ energy-dispersive X-ray diffraction. The results are important for understanding the structural features of bulk-forming glasses.     

Shape of prismatic dislocation loops in anisotropic α-Fe

Prismatic dislocation loops are the primary manifestation of radiation damage in crystals, and contribute to the phenomenon of radiation embrittlement. This undesirable effect, most serious for materials used in high-dose environments such as next-generation fission and future fusion reactors, results from the strong interaction between gliding dislocations, the carriers of plasticity, with the population of radiation-induced prismatic loops. Ferritic–martensitic steels, the most promising candidate materials for future high-dose applications, are based on iron and are known to become highly elastically-anisotropic at the high temperatures (>500°C) at which they must operate. In this article, we develop a novel modelling approach based on anisotropic elasticity theory to predict the shapes of prismatic loops in anisotropic crystals, paying particular attention to the technologically important case of α-iron. The results are compared with transmission electron microscope observations of the damage structure sustained by ultra-high-purity iron irradiated to a dose of approximately two displacements per atom.     

Relationship between the fatigue cracking probability and the grain-boundary category

In this paper, the probability of fatigue cracking along different kinds of grain boundary (GB) and persistent slip bands (PSBs) is considered in the light of data obtained by cyclic deformation of copper bicrystals and columnar crystals. It is found that, in copper bicrystals, fatigue cracks always nucleate and propagate along large-angle GBs, irrespective of whether the GB is perpendicular, parallel or inclined to the stress axis. On the contrary, for columnar copper crystals containing small-angle GBs, PSB-matrix interfaces become the preferential sites for initiation of fatigue crack; fatigue cracking along the small-angle GBs was never observed. For a special [1-34]/[182^-7] copper bicrystal with a Sigma = 19b GB and a common primary slip plane, GB cracking also results in fatigue failure. Based on the results above, the interactions of dislocations carried by PSBs with GBs, including 'pile-up of dislocations', 'passing through of dislocations' and 'partial passing-through dislocations', are discussed. It is suggested that the probability of fatigue cracking in fatigued copper crystals increases in the order of small-angle GBs, PSBs and large-angle GBs.     

Retention and thermal desorption of helium in amorphous and crystalline FeBSi alloys

Helium retention in metals is related to their atomic structure and the type of defects they contain. In order to investigate the dependence of helium retention on structure, amorphous Fe₇₉B₁₆Si₅ and crystalline FeBSi alloys were irradiated by helium ions at room temperature. In the crystalline alloy irradiated with 5 keV He⁺ ions, three types of helium trapping sites were found: surface defects produced by the irradiation, interstitial-type dislocation loops, and voids. Although these defects did not exist in the amorphous FeBSi alloy, we did observe thermal desorption peaks related to all three types. In addition, helium was released during the crystallization of amorphous FeBSi that had been irradiated by He⁺ ions.     

Influence of the restored work-hardening rate on ductility studied by X-ray computed tomography

Abstract

Void growth and coalescence in a model material containing an artificial three-dimensional void array (the estimated local void volume fraction was 1.1%) were investigated by X-ray computed tomography (=XCT). The initially tapered cylindrical voids became elongated along the principal straining direction by some amount of tensile plastic deformation, and then the work-hardening capacity in the intervoid matrix was restored by an intermediate annealing. The annealed model material was pulled in tension all the way up to fracture to see if the existing void coalescence models can predict the void coalescence strain.     

Muscle Damaging Exercise Affects Isometric Force Fluctuation as well as Intraindividual Variability of Cognitive Function

Healthy untrained men (N = 11) were asked to perform 10 series of 12 repetitions of knee eccentric extension (EE) at 160° per second. Quadriceps muscle torques evoked by electrical stimulation at 20 Hz (P20) and 100 Hz (P100), maximal voluntary isometric contraction torque (MVC), maximal isokinetic concentric torque (IT) at 30° per second, voluntary activation index (VA), simple reaction time (RTs), complex reaction time (RTc), and torque variability at 30% of MVC were measured before EE, immediately after EE, and 60 min and 24 hr after EE. MVC, IT, P20, P100, and VA decreased significantly after EE and remained depressed 24 hr later. Torque variability increased significantly after EE. Average RTs and RTc did not change after EE, whereas intraindividual variability in RTs and RTc increased significantly after EE.     

Radial bisection of words and lines in right‐brain‐damaged patients with spatial neglect

The bisection of lines positioned radially (with the two ends of the line close and far, with respect to the participant's body) has been less investigated than that of lines placed horizontally (with their two ends left and right, with respect to the body's midsagittal plane). In horizontal bisection, patients with left neglect typically show a rightward bias for both lines and words, greater with longer stimuli. As for radial bisection, available data indicate that neurologically unimpaired participants make a distal error, while results from right‐brain‐damaged patients with left spatial neglect are contradictory. We investigated the bisection of radially oriented words, with the prediction that, during bisection, linguistic material would be recoded to its canonical left‐to‐right format in reading, with the performance of neglect patients being similar to that for horizontal words. Thirteen right‐brain‐damaged patients (seven with left spatial neglect) and fourteen healthy controls were asked to manually bisect 40 radial and 40 horizontal words (5–10 letters), and 80 lines, 40 radial and 40 horizontal, of comparable length. Right‐brain‐damaged patients with spatial neglect exhibited a proximal bias in the bisection of short radial words, with the proximal part corresponding to the final right part of horizontally oriented words. This proximal error was not found in patients without neglect and healthy controls. For bisection, short radial words may be recoded to the canonical orthographic horizontal format, unveiling the impact of left neglect on radially oriented stimuli.     

Effect of low dose ionizing radiation exposure in utero on cognitive function in adolescence

Heiervang, K. S., Mednick, S., Sundet, K. & Rund, B. R. (2010). Effect of low dose ionizing radiation exposure in utero on cognitive function in adolescence. Scandinavian Journal of Psychology, 51, 210–215. Radiation from the Chernobyl nuclear power plant meltdown greatly affected several Norwegian counties. The cognitive consequences of in utero exposure to radiation from the Chernobyl accident have been intensely debated. This study examines the cognitive outcomes for those Norwegians who were exposed as fetuses to the fallout from Chernobyl. The participants, 84 adolescents who were exposed in utero to radiation from the most contaminated areas in Norway and 94 adolescents from areas not contaminated by the radiation, were tested on verbal and nonverbal IQ. Two data analyses were conducted. First, using a control‐group design, the IQ scores of exposed and unexposed adolescents were compared. Second, in a timing‐of‐exposure design, those exposed during the most sensitive period were contrasted with those exposed later in gestation. Adolescents exposed to low‐dose ionizing radiation in utero scored significantly lower in full‐scale IQ than unexposed adolescents. The difference was restricted to verbal IQ and was not evident for nonverbal IQ. The effect was not observed in exposed adolescents who had passed the most sensitive gestational period prior to the accident and thus were exposed to the radiation from Chernobyl exclusively after gestational week 16. These participants performed as well as the controls. Although the results should be interpreted cautiously due to the study’s nonrandomized design, the data add new and important support to the hypothesis that the Chernobyl accident may have had a subtle effect on the cognitive functioning of those exposed to low‐dose ionizing radiation in utero during the most sensitive gestational period.     

试论骨科辐射效应的线性与非线性关系

放射界对于辐射效应一直沿用线性无阈理论,但近年来,低剂量辐射效应却让其表现出非线性特征。而且对于骨折以及骨科其他疾病来说不同剂量辐射所产生的效应是不同的,即其在骨科中也存在线性与非线性的对立统一,只有认清这两者的辩证关系,才能抓住其本质,最终产生深远的意义和临床应用。     

Terror and Collateral Damage: Are they Permissible?*

This article begins by comparing terror and death and then focuses on whether killing combatants and noncombatants as a mere means to create terror, that is in turn a means to winning a war, is ever permissible. The role of intentions and alternative acts one might have done is examined in this regard. The second part of the article begins by criticizing a standard justification for causing collateral (side effect) deaths in war and offers an alternative justification that makes use of the idea of group liability. * This article is a shortened version of my “Failures of Just War Theory: Terror, Harm, and Justice,” Ethics 114 (July 2004), pp. 650–694, with the addition of new material on the use of terror in Section 2.